In recent years, one such function which is installed in a storage apparatus that has been attracting attention is a virtualization function known as ‘Thin Provisioning.’ A Thin Provisioning function is a function which provides a host computer with a virtual logical volume (referred to hereinbelow as a virtual volume), and which, when a request to write data to the virtual volume is issued by the host computer, dynamically assigns a storage area to the virtual volume. The thin provisioning function is advantageous in providing the host computer with a virtual volume with a larger capacity than the storage area that is actually available and in affording the construction of a low-cost computer system by reducing the physical storage capacity in the storage apparatus to be pre-prepared.
Furthermore, as a data management method for this kind of storage apparatus with a built-in thin provisioning function, a hierarchical-type data management method has conventionally been proposed. A hierarchical-type data management method is a method in which storage areas provided by each of a plurality of types of storage devices of varying performance which are built into the storage apparatus are managed as storage tiers of a plurality of different types, where storage areas are assigned from a high-speed, high-performance storage tier to areas where data of high access frequency in the virtual volume is stored, and storage areas are assigned from a low-speed, low-performance storage tier to areas where data of low access frequency in the virtual volume is stored. With this hierarchical-type data management method, the cost performance of the storage apparatus can be improved.
PTL1 discloses technology relating to the foregoing hierarchical-type data management method. More specifically, a storage control apparatus collects access information relating to access to each of the logical disk devices and presents this access information to the maintenance manager. If a relocation instruction is received from the maintenance manager, the storage control apparatus relocates physical disk devices between two logical disk devices in response to this relocation instruction, and continuously revises the storage of all data to the relocated physical disk devices.